sour gourd

definition: acid-tasting Australian gourd-like fruit with a woody rind and large seeds
example:
speech part: noun
synonyms:
definition: African gourd-like fruit with edible pulp
example:
speech part: noun
synonyms: monkey bread
definition: Australian tree having an agreeably acid fruit that resembles a gourd
example:
speech part: noun
synonyms: cream-of-tartar tree

How sour gourd is being used?